Showing papers on "Electromagnetic coil published in 1983"

Uniform magnetic field produced by three, four, and five square coils

Abstract: The optimal dimensions of thin coil systems of three and four square coils for producing uniform magnetic fields are calculated We find that for three square coils, of side d and separation s between the outer coils, the most uniform field distribution occurs with s/d=0821 116 and with I′/I=0512 797 I′/I is the ratio of the currents in the center coil to that of the outer coils With four square coils, the best uniformity is obtained when a/d=0128 106 and b/d=0505 492, where a is the distance from the center to the inner coils and b is the distance from the center to the outer coils The ratio of the current in the inner pair of coils to that in the outer pair must be I′/I=0423 514 We compare the uniformity of the field produced by these coil systems with each other and with Rubens’ five‐coil system, both on and off axis It is shown that the optimal four‐coil design is superior to the three‐ and five‐coil systems The sensitivity of the uniformity to the precision of construction is discussed Di

Radio frequency field coil for NMR

Abstract: An NMR radio-frequency coil is made up of a plurality of conductive segments evenly spaced about the peripheries and interconnecting a pair of conductive end-cap elements. Each conductive segment includes at least one reactive element which may include a variable capacitive or inductive element.

Analysis of resonant coupled coils in the design of radio frequency transcutaneous links

Abstract: A theory of coupled resonant coils has been developed which makes possible the design of radio frequency transcutaneous links of simultaneously high overall efficiency and good displacement tolerance while keeping circuitry simple (particularly in the implanted receiver). Series-tuned transmitter coils were used, obtaining high efficiency. In the first example a stimulator which has excellent displacement tolerance because it works at critical coupling is designed. The second example shows how the theory was used when the voltage in the implant was regulated. The design process involvesad hoc compromises between disparate quantities (e.g. efficiency against voltage transfer ratio), rendering a standard design procedure unsuitable. Fortunately, the derived theoretical formulae are simple enough for every design to be considered from fundamentals, based on coil parameters. Extensive coil loss data are presented here for the frequency band 0·2 to 20 MHz.

Fault current limiter using a superconducting coil

Abstract: A novel circuit, consisting of solid-state diodes and a biased superconducting coil, for limiting the fault currents in three phase ac systems is presented. A modification of the basic circuit results in a solid-state ac breaker with current limiting features. The operating characteristics of the fault current limiter and the ac breaker are analyzed. An optimization procedure for sizing the superconducting coil is derived.

General theory of fast-fronted interturn voltage distribution in electrical machine windings

Abstract: Motor-coil failure caused by high interturn stressing can occur because of the application of fast-fronted switching surges to the stator winding. It is shown that a new method of analysis of surge propagation in coils is necessary. A generalised method of analysis, which is capable of predicting voltage distribution in coils due to fast-fronted surges, is developed. The analysis, omitting losses, gives results which are significantly more accurate than those previously published. Further development of the analysis to include losses is also given. A comparison of measured results and results predicted by the lossy model shows the model to be extremely accurate. It is demonstrated that surges propagate through coils in both a series and a parallel manner and that each mode of propagation cannot be treated separately. (See also WRIGHT, M.T., YANG, S.J., and McLEAY, K.: `The influence of coil and surge parameters on transient interturn voltage distribution in stator windings′, IEE Proc. B, Electr. Power Appl., 1983, 130, (4), pp. 257-264.

30-MJ superconducting magnetic energy storage system for electric utility transmission stabilization

Abstract: A superconducting magnetic energy storage (SMES) system has been built to damp power oscillations on the Western U.S. Power System, particularly on the Pacific AC Intertie that is used to transmit power from the Northwest to southern California. The 30-MJ superconducting inductor that stores energy for this purpose is contained in a nonconducting dewar and is supported by a helium refrigerator and a gas-handling system mounted on trailers. Energy flows in and out of the inductor at frequencies from 0.1 to 1.0 Hz with power amplitudes up to 11 MW. The principal oscillation to be damped has a characteristic frequency of 0.35 Hz. The superconducting coil maximum current is 5 kA with terminal voltages up to 2.2 kV. The coil interfaces with the Bonneville Power Administration 13.8-kV bus at the Tacoma Substation through a converter and transformers. The system can be operated with the converter either in parallel-bridge mode or for constant VAR control with the bridges in buck-boost mode. The program for the design, fabrication, installation, and the preliminary experimental operation of the system is reviewed.

Two-dimensional precise positioning device for use in a semiconductor manufacturing apparatus

Abstract: A precision positioning device particularly adapted for use in a semiconductor manufacturing operation is provided which comprises a loading table, an armature and a two-dimensional current-motion converter having a magnetic field group and a first coil group. The magnetic field group is formed from a plurality of magnetic fields disposed on a plane in a two-dimensional array. The centers of the magnetic fields of the array are separated by an equal period. The magnetic fields of the array are disposed perpendicular to the plane and adjacent magnetic fields are directed in alternate directions. The first coil group comprises at least first, second, third and fourth coils having a fixed dimensional relationship. More particularly, each coil is provided with an outer dimension approximately equal to three halves of the magnetic fields and a coil width approximately equal to one-half of the period of the array. The four coils are separated along the plane by separation distances which equal an odd multiple of approximately one-half of the period of the array of magnetic fields.

Helical coil for diathermy apparatus

Abstract: A deep-heating diathermy apparatus consisting of a hollow tube adapted to receive a part of the body, or other dielectric material to be treated. An rf coil coaxially surrounds the tube and is driven by an rf generator. The total wire length of the coil is approximately 0.7 to 1.3 (depending on specific electrical properties and volume of the treated material) times the wavelength of a basic driving frequency provided by the generator. The output of the generator is supplied to the coil via a 50-ohm coaxial cable and a matching impedance. The coil may be driven by frequencies corresponding to integral multiples of one-half the basic wavelength, to enable shifting the heat focus volume along the coil axis from the normal centered location on the axis produced by full-wave excitation.

Inherent delay line ultrasonic transducer and systems

Abstract: An ultrasonic transmitting and/or receiving transducer is disclosed which includes a piezoelectric body with electrodes at opposite faces thereof. At least one of the electrodes is in the form of an elongated strip conductor such that the transducer also functions as a lossy delay line. The beam pattern of the transducer is dependent upon the delay of the delay line. A high permeability member such as a ferrite body is located adjacent the elongated strip conductor to increase the distributed inductance of the delay line and, consequently, the delay thereof. The permeability of the ferrite body is controlled by use of a drive coil adjacent thereto. By time varying the drive current to the coil, the acoustic beam pattern is time varied. By using a spiral shaped elongated strip conductor on a cylindrical shaped piezoelectric body, a focusing transducer is provided.

Angular position sensor

Abstract: An angular position sensor comprising a generator coil driven by an oscillator to provide an alternating magnetic field which is symmetrical about an axis, an annular rotor of electrically-conductive or magnetic material such that it distorts the magnetic field around it and arranged so that it is asymmetrical about its axis of rotation and lies outside the equatorial plane of the magnetic field and two sensing coils disposed within the magnetic field. As the rotor 16 rotates about its axis the emfs induced in the sensing coils vary in dependence upon the angular position of the rotor relative to the axis of the undistorted magnetic field.

Vehicle battery charging apparatus.

Abstract: An apparatus (10) for delivering electrical energy from a charging station (12) to a vehicle (14), for example, to charge a vehicle battery (16). The apparatus (10) includes vehicle and station bumpers (18, 20) each associated with a respective wire coil (28, 24), and forming respective flux path elements for the coils (28, 24). Means (34) are provided for sensing the relative position of the first and second coils (24, 28) and controllably delivering the electrical energy in response to the sensed position. Third and fourth coils (80, 82) provide two-way communication between the station (12) and the vehicle (14), and blocking means (96) facilitates removal of the vehicle (14) from the station (12).

Dynamoelectric machine having a large magnetic gap and flexible printed circuit phase winding

Abstract: A dynamoelectric machine having a large magnetic gap and flexible printed circuit phase windings includes a multi-pole samarium cobalt magnet assembly consisting of radially aligned magnets and circumferentially positioned interpole magnets attached to a soft iron ring for providing radially directed magnetic poles of alternating polarity, and a printed circuit winding assembly attached to a soft back iron sleeve for providing electromagnetic poles. The printed circuit winding assembly comprises a lamination of selectively aligned and interconnected printed circuit phase windings, each having serially connected printed circuit coils of the same phase. The winding and magnet assemblies are separated by a small mechanical gap to allow their relative rotation. The magnets and soft iron structures are proportioned to operate near the maximum energy product condition for Samarium Cobalt, where the sum of the mechanical gap thickness and the winding assembly thickness is the magnetic gap in a high reluctance circuit. A large volume of windings is placed within the permanent magnet field and entirely within the magnetic gap to provide a large ampere-turn condition at a low power dissipation. Brushless DC single and multi-phase torquers, brush-type DC torquers, stepper motors, and synchronous motors embodying the dynamoelectric machine of the present invention are highly efficient devices having a very low magnetic drag torque and a magnetic cogging torque substantially equal to zero.

Electromagnet for NMR tomography

Abstract: An electromagnet for producing the constant magnetic field required in NMR tomography comprises a coil system (1, 2, 3, 4) of the Helmholtz double coil type. The coil system is enclosed in, and supported by, a stable cylindrical shell (5). The influence exerted by the cylindrical shell (5) on the homogeneity of the magnetic field, which is generated by the coil system in an accessible interior space defined by it and suitable to receive the body to be examined, is compensated by the particular dimensioning of the field and error coils (1, 2, 3, 4). The cylindrical shell (5) is best made of a ferromagnetic material having low electric conductivity and is constructed of a plurality of axially serially disposed annular discs (6) which are preferably divided into sectors.

Induction heating gun

Abstract: This device for inductively heating and fusing thermoplastics includes an alternating current passing through a tank circuit, the inductor member of the tank circuit being wrapped around a curved pole piece of a ferromagnetic material. The magnetic flux arising within the inductor coil member flows to the ends of the pole piece and into a screen placed between the materials to be joined. The flux induces a current in the screen, and heat is generated to melt the thermoplastics together. Because only 30-150 watts of power are passed through the tank circuit, a wire which will remain cool under operational wattage may be selected, making air or fluid cooling unnecessary.

Wave activated generator

Abstract: A wave activated generator utilizes the principle of providing relative movement between a permanent magnet and a coil to induce an electrical current in the coil. The coil is situated in a static tube anchored to the sea bed by means of a ballast tank at the base of the tube and guy wires extending from the tube. A plunger with permanent magnets is mounted in the tube for vertical reciprocation of the plunger, the plunger projecting outwardly from the upper end of the tube and terminating in a hull-shaped float which rides the water surface and provides vertical reciprocation of the plunger responsive to wave motion in order to move the magnets relative to the coil and generate current in the coil.

Counterfeit detection circuit

Abstract: A magnetic sensor including a coil for sensing a changing magnetic field developed by paper currency moving past the magnetic sensor. A capacitor forms a tuned circuit with the magnetic sensor coil to pass only those signals lying within a predetermined frequency range. A comparator compares the signals lying within the pass band with a predetermined threshold to determine the presence or absence of genuine currency. The tuned circuit significantly improves the signal to noise ratio of the sensing means and hence, significantly improves the ability to determine the genuineness of the currency. In a second embodiment, the presence of a magnetic field having a field strength above the predetermined threshold is utilized to pass timing pulses for clocking a counter. A decoder gate coupled to the counter indicates the presence of a genuine bill, only after a predetermined count has been reached. A reset circuit is provided for resetting the detecting circuitry immediately after each bill is examined and before examination of the next bill.

Apparatus and method for increasing the sensitivity of a nuclear magnetic resonance probe

Abstract: The discovery has been made that coil-to-ground parasitic losses substantially reduce the sensitivity of a nuclear magnetic resonance probe used in nuclear magnetic resonance analyses of lossy dielectic (i.e., relatively conductive) samples, such as biological tissue. A probe circuit is disclosed in which a balancing impedance is inserted for substantially reducing the influence of coil-to-ground parasitics. The probe circuit resulting from the insertion of the balancing impedance markedly increases sensitivity. Concomittantly, the quality factor of the probe circuit and the signal-to-noise ratio of nuclear magnetic resonance signals are substantially improved. The disclosed probe circuit can be incorporated in nuclear magnetic resonance analysis systems where the sample coil is either implanted or placed on the surface of a sample; where the sample coil forms a portion of a large-scale imaging system; or the sample coil is used in a traditional analytical mode with a sample contained in a glass tube.

High dielectric output circuit for electrosurgical power source

Abstract: A transformer circuit including a primary coil with first and second voltage divider segments arranged in phase with equal inductances and a plurality of taps on the second segment. A switch is used to selectably ground one of the taps for varying the voltage impressed on the second segment. The transformer also has a secondary coil including first and second voltage divider segments arranged 180° out of phase and having equal inductance. The secondary coil is heavily insulated, and the primary and secondary coils are coupled together to provide an output equal to the sum of the voltages applied to the segments of the secondary coil so that the transformer output can be varied by switching from one tap to another of the second segment of the primary coil and that the secondary coil can be heavily insulated and isolated from ground.

Combination transformer with common core portions

Abstract: A combination transformer with common yoke core characterized by the combination of a main transformer and series transformers, which transformers have separate and complete core and coil assemblies with a common core leg or yoke to reduce the core size, weight and loss.

Electric rotary machine with toroidal windings on an annular stator core

Abstract: An electric rotary machine provided with a toroidal winding has a stator core made of annular punched seamless laminations. Insulation members, each having partition plates, are mounted on the stator core. Crossover conductor portions interconnecting unit coils of the toroidal winding are retained and guided by the partition plates. The unit coils in each of the slots formed in the stator core are wound by a single continuous electrical conductor, to yield a machine of highly improved performance.

Transverse gradient field coils for nuclear magnetic resonance imaging

Abstract: In the production of nuclear magnetic resonance images, it is necessary to provide various magnetic fields with specified orientations and configurations in particular relationships with respect to a cylindrical coil form on which the RF and gradient coils are generally disposed. In particular, it is necessary to produce so-called transverse gradient fields which are oriented transversely with respect to the cylindrical form. It is necessary to produce a component parallel to the axis of the cylinder, but which component varies linearly in intensity in the direction transverse to the axis. That is to say, it is desirable to produce a magnetic field component within the cylinder such that surfaces on which this component is constant are parallel and are generally oriented parallel to the axis of the cylinder. Furthermore, for the purpose of providing proper spatial definition and resolution, it is necessary that this transverse field exhibit a highly linear variation in intensity inside the cylinder. In a nuclear magnetic resonance imaging system, two such coil sets are required and are oriented at right angles to one another so as to generate x-axis and y-axis positioning information. The present invention describes coil winding patterns which are capable of producing such transverse gradient magnetic fields with an exceedingly high degree of linearity.

Gradient-coil apparatus for a magnetic resonance system

Abstract: Apparatus for imposing a gradient magnetic field intensity on a static magnetic field intensity in a nuclear- magnetic-resonance (NMR) system The gradient field has a predetermined error relationship with respect to a desired characteristic of the gradient field within a selected region The selected region is substantially smaller in volume than the volume «enclosed» by a surface or surfaces on which electrical conductors are distributed to generate the gradient field The surface current densities in a grid-like pattern of differential areas on the surfaces are chosen such that, within the selected region, the predetermined error relationship results The gradient field intensity outside of the selected region generally does not have the characteristic desired within the region The predetermined error relationship can be established in a linearly-varying field intensity in a spherical volume enclosed by a cylindrical surface Generally hyperbolically-shaped electrical coils on the cylindrical surface can provide surface current densities required for a constant transverse-gradient (a linearly varying magnetic field intensity in a direction transverse to the axis of the cylinder)

Permanent magnet rotary dynamo electric machine

Abstract: A permanent magnet rotary dynamo electric machine wherein each permanent magnet pole (13) is equipped with a flux shunt (18) which provides a direct flux path between the airgap at the strong tip region of the pole and the iron circuit (12) upon which the pole is supported, the direct flux path shunting magnetic flux to the iron circuit when the current in the associated windings is low, but being saturated by flux flowing in the opposite direction at high values of winding current.

Optical deflecting element

Abstract: PURPOSE:To make a two-dimensional deflection scan through one element by supporting a galvano mirror with a gimbals spring, and controlling the application of magnetic fields in two X and Y directions while flowing a current to the thin film coil on a mirror surface. CONSTITUTION:A substrate 1 made of Si single crystal is worked into the gimbals spring by photoengraving. The gimbals spring 2 rotates and oscillates about an X-directional axis 5 and an Y-directional axis 6 independently. The galvano mirror 3 and thin film coil 4 are formed on the surface of the center movable part of the substrate 1 supported with the gimbals spring 2 by metal vapor deposition or plating. The constant current is supplied to the thin film coil 4 to vary a magnetic field 7 in the X direction and a magnetic field 8 in the Y direction independently of each other, and consequently the element rotates and oscillates about the axes 5 and 6 independently of each other with electromagnetic force, so that reflected light from the mirror 3 is deflected in two dimensions.

Non-contacting code recognition system for code carriers on production line workpieces

Abstract: To permit ready change of information on information carriers applied to workpieces which travel along a production line, for example to control further operating, machining or assembly steps, non-contacting sensors, typically inductive elements generating an electromagnetic field, transfer to a pick-up coil on the information carrier binary data. The information carrier includes a non-volatile permanent memory (ROM 25, 41) containing data characterizing the particular workpiece carrier or workpiece thereon, and a re-programmable, preferably non-volatile memory (RAM 27, 42) which contains added at the various operating stations to characterize operations, dimensions and the like of the respective workpiece and/or subsequent operations to be performed. The non-contacting transformer formed by the write/read stations and the pick-up coil (33, 47, 50) may, simultaneously, function as an energy transfer element to transfer operating energy for the memory units (23, 24, 40) on the workpiece carriers (11, 12) or the workpieces themselves (14, 15).

Pacing lead with insertable memory coil

Abstract: A body implantable lead which may be provided with a desired predetermined curve. A memory coil is inserted into the lead while straightened by a stylet. After removal of the stylet, the memory coil imparts the desired curve to the lead.

Frictionless valve/pump

Abstract: A valve having no friction producing components includes a flexible and resilient tube for carrying a fluid, an electrically energizable coil for producing an electromagnetic force when energized, a magnetically attractable element, and an elongate leaf spring attached near one end to the coil and looped outwardly, upwardly and back toward the coil, with the magnetically attractable element attached to the leaf spring near the other end. The leaf spring normally holds the magnetically attractable element out of contact with the coil, but when the coil is energized, the element is attracted towards the coil. The one end of the leaf spring attached to the coil is also formed to extend upwardly and over the magnetically attractable element to act as an anvil, and the other end of the leaf spring attached to the element extends upwardly towards the anvil to form a pinching tab. The tube is positioned between the anvil and pinching tab so that when the coil is de-energized, the tube is pinched closed between the tab and anvil. When the coil is energized, the element and pinching tab are attracted towards the coil and away from the anvil to release the tube and allow it to open.

Axial air gap brushless alternator

Abstract: A brushless alternator is disclosed having a stationary field coil and core surrounded by a stationary stator coil and core with a cylindrical air gap being defined therebetween A rotor assembly is fixed to a rotatable shaft and has interweaved separate magnetic finger assemblies joined together by a non-magnetic ring wherein these fingers are rotated in the cylindrical gap The stator and field cores are radially disposed with respect to the rotatable shaft The field core axially extends beyond the effective axial length of the field coil and provides at an axial position beyond the effective axial length of the field coil, at least one low reluctance axial flux gap between the field core and the magnetic fingers This flux gap conducts a substantial portion of the flux created by the field coil The field core also serves as a shaft bearing retainer and has a bearing grease reservoir comprising a cylindrical recess adjacent the shaft bearing

Electro-magnetic alignment assemblies

Abstract: This invention is directed to electromagnetic alignment apparatus, which is particularly adapted, among other possible uses, for use in aligning the wafers in a microlithography system, said apparatus comprising in combination a first magnetic circuit having a plurality of elements including a first magnet; a second magnetic circuit having a plurality of elements including a second magnet; the second magnetic circuit being disposed in spaced relationship with respect to the first magnetic circuit; a movable structural component adapted for mounting an object thereon; one element of each magnetic circuit being fixedly attached to the movable structural component; first and second current carrying coil assemblies mounted in the first magnetic circuit; the second coil assembly being disposed at an angle with respect to the first coil assembly; third and fourth current carrying coil assemblies mounted in the second magnetic circuit; the fourth coil assembly being disposed at an angle with respect to the third coil assembly; and control apparatus for controlling the flow and direction of the current through the coil assemblies, respectively.

Device for detecting metallic objects in a flow of non-metallic material

Abstract: A device for detecting metallic objects in a material flow, comprising as sensing member a scanning coil consisting of a primary coil and, for example, two oppositely connected secondary windings arranged symmetrically around the primary winding so that the voltage induced in the secondary winding becomes zero as long as no conducting objects appear in the scanning area. To eliminate irrelevant signals from conducting objects in the vicinity of the scanning coil but not in the material flow or from weakly conducting objects in the material flow, the primary winding is fed with at least two alternating currents having different frequencies. The corresponding secondary voltages are rectified in phase-controlled rectifiers, and in a calculating circuit the difference is derived between the output of one rectifier voltage and the output of another rectifier multiplied by a constant factor which includes the relation between the frequencies of the corresponding alternating voltages.